Dummy fuze



P 2, 1 c5. w. JOHNSON ETAL 2,849,956 DUMMY FUZE- Filed Feb. 26, 1957INVENTORS, I H Bent-Q's lfianuvski I I g] BY Ui'hnMJuhnsun sults.

United States Patent DUMlVIY FUZE Otho W. .lohnson and George J.Ganovski, Baltimore,

Md., asslgnors to the United States of America as represented by theSecretary of the Army Application February 26, 1957, Serial No. 642,624

3 Claims. (Cl. 102-70) (Granted under Title 35, U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes without the payment to meof any royalty thereon.

This invention relates to a dummy fuze, and more particularly to aninert device assembled to resemble a live fuze of the type carried bythe projectile fired from the 120 mm. automatic gun having automaticfuze setting equipment.

Dummy fuzes are attached to target practice ammunition where a fullfunctioning fuze is not required. Fuzes of this type may be fabricatedfrom burned out or rejected inert parts of service fuzes, ormanufactured especially for the purpose for which they are intended.Whether fabricated from disused parts or especially manufactured, theassemblies are completely inert. In general, the fuzes are intended tosimulate a specific model, or one type of service fuze. The contour andweight of the service fuze which is to be simulated are approximatedclosely in the dummy fuze for use with practice ammunition, and to givethe proper feel when used with drill ammunition. This policy alsopermits the use of drill ammunition in conjunction with fuze setters fortraining in preparing ammunition in conjunction with fuze setters forfiring and in servicing the piece. Most dummy fuzes are extremely simplein construction but essential features of the simulated service fuze areincorporated in some types.

Heretofore, existing dummy fuzes for use with the 120 mm. projectilehave produced unsatisfactory re- After being used for only three or fouroperations, these fuzes became unserviceable due to wear and tear atpoints of adjustment and thereby incurred great expense through thenecessity of providing a large number of dummy fuzes.

This wear and tear upon the dummy fuzes is caused chiefly by theiremployment in checking the M18 and M19 automatic fuze setters. Fuzes ofthis type generally have a base upon which the time setting indicia isengraved. A rotatable lower cap is rigidly secured to an upper cap forrotation as a unit therewith. On the lower cap and on the base, there isprovided a setting grove, one each, into which the setting jaws of thefuze setter fits in order to rotate the lower cap in a clockwisedirection to the desired time delay setting for arming. The groove inthe lower cap is subject to more wear than the groove in the base due tothe fuze setter moving the lower cap. Another point of wear is thesafety set screws usually found on fuzes of this type. The screwsprevent rotation between the base and lower cap during handling and thepossibility of premature arming of the fuze. After a very short periodof use, wear at these points rendered the fuze useless and it wasnecessary to either replace the lower cap or obtain a new assemblyentirely. With the present invention, it is proposed to eliminate theseobjectionable features by providing a readily replaceable insert ofhardened tool steel to replace the existing setting groove and to iceincorporate the set screws in a setting groove cut in the insert, thusproviding long and continuous. use of the fuze. It is further proposedto provide an adjustable means to provide the proper torque between thebase and the rotatable lower cap portions of the fuze.

It is therefore a principal object of this invention to provide a dummyfuze capable of long and continuous use.

It is another object of the invention to provide a dummy fuze for use byanti-aircraft units in training for checking the M18 and M19 automaticsetters.

A further object is to provide a fuze having a replaceable hardened toolsteel insert at the area of the set screws holding the rotatable partsof the fuze and to provide adjustable torque means to provide relativerotation between the fuze setting elements. of the fuze.

The invention will be best understood from a consideration of thefollowing detailed description taken in connection with the accompanyingdrawing, it being understood however, that the invention is not limitedby the specific illustration or description but that uch illustrationand description constitutes a preferred embodiment of the invention.

In the drawing: I

Fig. 1 is a longitudinal section taken along line 11 of Fig. 2,illustrating in assembled relation the dummy fuze of the invention,

Fig. 2 is a side elevation of the fuze,

Fig. 3 is a detail section taken along line 3-3 of Fig. 2, and,

Fig. 4 is a perspective view of the hardened metal insert.

Referring more particularly to the drawings in which 1 indicatesgenerally a dummy fuze constructed in accordance with the inventionhaving a base member generally indicated as at 2, a lower cap memberindicated generally by 3 and an upper cap 4. Base 2, lower cap 3 and theupper cap 4 are identical to the parts of the fuze which the fuze of theinvention is intended to simulate. The base 2 comprises an annular bodyhaving a rearward externally threaded portion 5 for attachment to aprojectile (not shown) when desired, an intermediate forwardly taperingportion 6 of larger diameter than portion 5 constituting the timesetting ring of the fuze and a forwardly reduced portion 7. The base 2is provided with a rearward axial bore 8, a forward axial bore 9 and areduced axial bore 10 communicating between the forward and rearwardbores. The lower cap 3 comprises an annular member having a forwardlytapered rearward portion 11 and a forwardly extending externallythreaded portion 12. The lower cap 3 is provided with a rearward axialbore 13, of a diameter to permit the reduced portion 7 of the base 2 torotate therein, a forward axial bore 14 and an intermediate reducedaxial bore 15 communicating between bores 13 and 14. The upper cap 4which servesv as the windshield is internally threaded as at 16 at itsrearward end and is adapted to threadably engage the threaded portion 12of lower cap 3 for rotation therewith.

Adjustable means are provided to apply sufiicient torque between thebase and the lower cap for relative rotational movement therewith andconsists of a cap screw 17, flanged adapter bushing 18, Bellevillespring 19, a pair of fiat washers 20 and 21 and safety nuts 22. Thesemembers are assembled in the manner illustrated in Fig. 1. The flangedadapter bushing 18 fits into the bore 15 and has an axial bore 23 of thesame diameter as bore 10, both bores 10 and 15 adapted to receive thecap screw 17. Means preventing wear in the setting groove of the lowercap 6 and safety screws is provided which consists of a mortise 24 (seeFig. 3) cut in the giving long and continuous use.

rearward portion of the peripheral surface of lower cap 3. Mortise 24 isintended to replace the existing setting groove in the lower cap and islocated exactly in this area. An insert 25 of hardened tool steel fitssnugly within the mortise 24 and is provided with a setting groove 26.As the tool setter to be employed for this type of fuze is rotatedclockwise insetting the fuze,

the lands of the insert are of different heights. The left land 27 iscut lower than the land 28 to provide a vertical face 29 for engagementwith lugs on a fuze setter (not shown) to engage, thu insuring only aclockwise movement of the lower cap. Threaded holes 30 are provided inthe floor of the setting groove'26 and are counter bored as at 31 toprovide a planar surface to the groove 26 receiving screws 32. Suitableindicia 33 is etched on the tapered surface of the base member 2 and asetting mark 34 is etched on the lower cap (see Fig. 2) which serves asthe time training ring of the fuze. The base member 2 is also providedwith a setting groove 35 for use when setting the fuze by automaticsetters.

In operation, the torque means may be adjusted by turning the cap screw17 to provide the amount of torque for the rotation between the lowercap 3 and base 2. If it is desired, the fuze may be screwed to aprojectile after the torque adjustment has been completed. As theramming and setting operation of the automatic 120 mm. gun arecompletely automatic and the setting desired is transmitted by adirector to the fuze setter electrically, no hand setting is necessary.The jaws of the fuze setter (not shown) will fit into setting grooves 26and 35 and will automatically rotate the lower cap about the base untilthe predetermined setting for time delay is reached.

The fuze of the invention is also adaptable to practicing hand setting.In this operation a hand setter (not shown) is applied on the lower capuntil its lug engages the setting groove 26 and the bore may be heldagainst rotation with a fuze wrench (also not shown) by engaging whenchgrooves 36 in base 2. The lower cap is then turned with one hand whilethe other hand holds the base against rotation by the fuze wrench untilthe mark 34 registers with the desired index line of the indicia 33.

It is apparent from the foregoing that a highly practical training fuzehas been devised which is capable of The fuze of the invention hasprovided a training fuze that is easily adjustable for torque to providethe right amount of force to be applied to rotation in setting the fuze.As the fuze has eliminated wear and tear at the points of manipulation,an almost indestructible training device has been attained.

It is to be understood that the form of the invention herewith shown anddescribed, is to be taken as a preferred example of the same, and thatvariou changes to a projectile, a rotatable lower cap and an upper caprigidly secured to said lower cap, said base having forward and rearwardaxial bores and a reduced axial bore communicating between said forwardand rearward bores, said cap having forward and rearward axial bore anda reduced axial bore being of larger diameter than said reduced bore insaid base, and means for securing said base and said rotatable lower capin coaxial relation comprising a flanged bushing having a bore ofsubstantially the same diameter as said reduced bore in said base, a capscrew received in said reduced bore in said base and said bore in saidbushing and means for providing adjustable rotational torque between aidbase and said lower cap comprising an adjustable nut threadably engagingthe forward end of said cap screw and a Belleville spring disposed onsaid cap screw between said flanged bushing and siad nut.

2. In a dummy fuze, a base for attachment to a projectile, said basedefining a forwardly extending annular reduced portion, a lower capadapted to receive the forwardly extending reduced portion of said basefor rotation therein, an upper cap rigidly secured to said lower cap forrotation therewith, pivot for said lower cap centrally disposed withinsaid base and said lower cap holding said base and said lower cap incoaxial alignment and said lower cap for rotation about said reducedportion on said base and a hardened metal insert adapted to be insertedin a mortise provided in the rearward peripheral surface of said lowercap, said insert being milled to define a longitudinal setting groovehaving a planar floor and smooth vertical side walls, the height of onewall being less than the other said highest wall to provide a fuzesetter engaging surface, said insert being bored and counterbored toreceive set screws piercing said lower cap to engage the peripheralsurface of said reduced portion on said base.

3. In a dummy fuze having a longitudinal axis of symmetry, a base memberfor attachment to a projectile, a rotatable lower cap, an upper caprigidly attached to said lower cap for unitary rotation therewith, pivotmeans securing said base and said lower'cap in coaxial alignment and forrotation about said base, said means being disposed axially within saidbase, a spring adjustably associated with said pivot means to permit theapplication of relative rotational torque between said lower cap andsaid base and a detachable fuze setter engaging member adapted to bereceived in a mortise provided in the rearward peripheral surface ofsaid lower cap.

References Cited in the file of this patent UNITED STATES PATENTS1,707,414 Pfafi Apr. 2, 1929 2,262,068 Towner Nov. 11, 1941 2,397,055Sekella Mar. 19, 1946 2,461,793 Whitehead Feb. 15, 1949 2,709,963Butterworth June 7, 1955

